Field of the Invention
The present invention relates to an image reading apparatus configured to effectively detect an abnormal pixel that is not present in an image of an object when the image is read, and to a method for processing an image read by the image reading apparatus.
Description of the Related Art
As an image reading apparatus to be used in a copying machine or the like, there is known an image reading apparatus configured to perform “flow-reading”. In the flow-reading, while originals are conveyed one by one onto an original table glass, each original is exposed with light emitted from a light source fixed at a predetermined position for image reading. At the time of the flow-reading, when foreign matter, for example, dust adheres to the original table glass, a streak image may be formed in the read image. In order to solve such a problem, hitherto, there have been proposed a technology of automatically detecting dust adhesion when dust has adhered onto the original table glass, to thereby urge a user to clean the original table glass, and a technology of performing correction through image processing.
For example, an apparatus disclosed in Japanese Patent Application Laid-open No. 2004-328200 is configured to convert the read image into binary data, and add the binary data for each line in a sub-scanning direction, to thereby detect a black streak when the addition result is equal to or more than a predetermined value. When the black streak is detected, the image is corrected.
In the apparatus disclosed in Japanese Patent Application Laid-open No. 2004-328200, when the read original has a vertical line like a ruled line extending in the sub-scanning direction, the ruled line may be falsely detected as a black streak.
The present invention has a primary object to provide an image reading method capable of detecting an abnormal pixel with high accuracy.